Throughout the specification, the terms "forward" and "rearward" are to be understood as referring to "in the direction to the front of the vehicle and subject seat" and "in the direction to the rear of the vehicle and subject seat", respectively and "upward" and "downward" to be taken as upward and downward with respect to the vehicle and subject seat, respectively.
It is desirable to equip a vehicle seat with a so-called "adjustable lumbar supporter" mounted in the backrest of the seat in order to increase riding comfort and minimize occupant fatigue. However previously proposed lumbar supporters are inevitably manually operated. In fact, the adjustment of the supporter is made by manually operating or handling a control knob which is usually fixed to an upper-side portion of the seat backrest. Thus, to an occupant sitting on the subject seat, it is troublesome to handle the control knob because the occupant must stretch his or her hand awkardly, backwardly and upwardly to the upper-side portion of the backrest.